Improved lubricating composition



novnn LUBRTGATENG coirrosrrrort Alfred H. Matuszair, Westtield, and Wiiiiam .i. Craven,

Elizabeth, N. 1., assignors to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Application Aprii 9, 1956 Serial No. 576,766

6 Claims. (Cl. 252--32.'7)

This invention relates to improved lubricating compositions useful for the lubrication of moving metal parts of reciprocating gasoline engines. Particularly, the invention relates to high viscosity index multi-viscosity grade motor oils having reduced deposit forming tendencies. Moreparticularly, the invention relates to improved high viscosity multi-grade lubricating compositions having combined therein a minor, but deposit formation tendency reducing amount of C C highly branched chain alcohol esters of polylinoleic acid.

A major change in the type of lubricating oil used for servicing gasoline powered reciprocating engines is taking place in the industry. The trend in motor oil use is to high viscosity index multi-viscosity grade oils. Although oils covering more than one viscosity grade have been marketed for many years, the newer oils are more versatile and offer additional advantages to the motorist.

The high viscosity index multi-viscosity grade oils differ from previous multi-grade oils in that they are made from a very light base stock with a large amount of viscosity index improver. Their principal advantage over the conventional motor oil is based on the use of a light base stock; they do not form heavy combustion chamber deposits, and therefore minimize octane requirement increase.

A second advantage of the new oils is their extremely high viscosity index, within a range of from about 140-155. Because of this low rate of change of viscosity with temperature (high viscosity index) they can combine the cold starting characteristics of a winter grade oil with theengine protection and low consumption characteristics of'a summer grade oil and can, therefore, be used as a year-round lubricant. Their high viscosity index also leads to better gasoline mileage under certain conditions, mainly under pre-Warrnup driving conditions. At these lower temperatures the new oils are less viscous, give less friction and therefore permit better fuel economy.

It has been found, however, that these high viscosity index multi-viscosity grade lubricating oils have one disadvantage over conventional oils. These light base stock oils have been found to cause deposit formation on the under side of the intake valves of reciprocating engines. Although the exact mechanism of the deposit formation is not clearly known, it is believed to be due to the combined eifect of the additive system used in the high viscosity index oils.

It has now been found that this undesirable deposit forming tendency of high viscosity index multi-viscosity grade lubricating oils can be reduced or eliminated by combining with these oils a material which is selected from the group of highly branched chain C to C alcohol esters of polylinoleic acid. Particularly suitable are the C to C branched chain alcohol esters of the dimer and the trimer of linoleic acid.

The dimer of linoleic acid, hereinafter referred to as dimer acid, is a high molecular weight dibasic acid formed by the Self-condensation of two molecules of linoieic 2,849,399 Patented Aug. 26, 1958 ice acid in a typical Diels-Alder reaction. The formation of dimer acid may be illustrated as follows:

5 HOC-(CHi)-1CH=CH (cum-H3 HO OH Another molecule of the linoleic acid may condense with one mole of the dimer acid to form the trimer of O linoleic acid, hereinafter referred to as trimer acid. Dimer and trimer acids are well known materials in commerce.

To form the materials which have utility in the practice of this invention, the dimer or the trimer acid is esterified with highly branched chain aliphatic primary alcohol-s having from about 7 to 14 carbon atoms or mixtures of such alcohols. The chain lengths of the alcohols chosen to esterify the acids are regulated by Viccosity considerations. Esters having been prepared from alcohols with more than about 14 carbon atoms usually 3 are too viscous and those having less than about 7 carbon atoms too thin to result in final compositions that have viscosities within the required range.

Especially suitable for preparing the esters useful in practicing this invention are the alcohols prepared by the well-known Oxo process. These Oxo alcohols are isomeric mixtures of branched-chain saturated aliphatic primary alcohols. In this process an olefin having one less carbon atom than the desired alcohol is subjected to a carbonylation reaction at a pressure within a range of from about 1000 to about 3000 pounds per square inch and at a temperature within a range of from about 300 to 400 F. in the presence of carbon monoxide and hydrogen. A carbonylation catalyst, such as a heavy metal carbonyl, e. g., cobalt carbonyl, is used. The aldehyde resulting from the carbonylation reaction is then hydrogenated in the presence of a hydrogenation catalyst to the desired alcohol.

Specific examples of 0x0 alcohols useful in the present invention for preparing esters of polylinoleic acid include C 0x0 alcohols, C 0x0 alcohols and C 0x0 alcohols. These particular Oxo alcohols are prepared, respectively, by oxonation (i. e., carbonylation plus hydrogenation) of propylene-hutylene copolymer, tripropylene and tetrapropylene and are predominantly mixtures of dimethyl hexanols, trimethyl heptanols and tetramethyl nonanols, respectively. The ratios of methyl groups to the number of carbon atoms in the longest straight chains are 0.33, 0.43 and 0.44, respectively, for these particular OX0 alcohols. More highly branched Oxo alcohols than those mentioned above may also be employed in the practice of the present invention. For example, a C Oxo alcohol obtained by the oxonation of diisobutylene is predominantly tetramethyl pentanol having a ratio of methyl groups to the number of carbons in the longest straight chain of 0.8. In the present specification, it will be understood that the term branched chain alcohol is one whose branches consist of methyl groups in the ratio of from 0.33 to 0.8 methyl groups to the number of carbon atoms in the longest straight chain.

7 The following table, for example, shows the structure and percent composition of C OX0 alcohols prepared from a C olefin stream which had been fractionated from the products obtained by the phosphoric acid polymeriza- Lil tion of refinery gas streams containing propylene and mixed nand isobntylenes.

It will be noted that the above C Oxo alcohol is predominantly a mixture of 3,5-, 4,5- and 3,4-dimethyl hexanols.

To illustrate the preparation of the materials useful in the concept of this invention, the following example is given. In this illustrative example, a highly branched chain primary C alcohol mixture formed by the carbonylation and hydrogenation of a C olefin obtained by copolymerization of propylene and butylene is used as the alcohol. This C OX alcohol has been described in detail heretofore. The dimer acid used is commercially available under the trade name Empol 1022 Polymerized Fatty Acid and contains about 17% of trimer acid.

In the preparation of C Oxo dimerate, 234 g. (1.8 moles) of C Oxo alcohol were reacted with 450 g. (0.75 mole) of Empol 1022 in the presence of 3 g. NaHSO catalyst and 50 g. heptane (as water entrainer). After 1 hour refluxing at a maximum temperature of 193 C., the material was filtered from the catalyst and then stripped to a liquid temperature of 225 C. at 1 mm. pressure. The product weighed 617 g. (yield, 97.5%) and had the following properties:

Other esters of dimer acid (Empol 1022) and of trimer acid were made in a similar manner.

The esters of this invention are combined with the high viscosity index multi-viscosity grade lubricating oils in amounts varying from about 0.5 to 30.0%, preferably about 1.0% to 15.0%, percentage being based on the weight of the total composition. As was stated above, the amount used will depend upon the viscosity of the ester and the viscosity desired in the final blend.

The base oil used to formulate the compositions of this invention, that is to say, the high viscosity index multi-viscosity grade lubricating oil, comprises a low viscosity mineral oil base stock and an additive system. The additive system is ordinarily made up from a detergent inhibitor, an antioxidant, a pour point depressor,

and a viscosity index improver. The components of the composition will be more completely defined below.

THE MINERAL OIL BASE As was pointed out above, the base stock. used in the preparation of the high viscosity index multi-viscosity grade mineral oils is primarily a light base stock that is free of high boiling heavy ends. Refined mineral oil distillates obtained from paraflinic or naphthenic-base crude oils and boiling within the range of about 300 to 700 F. (more preferably 375675) at 10 mm. Hg absolute are preferred as the base stocks for the materials of this invention. These preferred base stocks are low in combustion chamber deposit forming tendency as evidenced by their low resinification indices. This measure of combustion chamber deposit formation tendency is set out in detail in S. N. 352,373, filed on May 1, 1953, now issued as U. S. Patent 2,761,766. The mineral oil base stock operable herein should have a resinification index below about 20 mg./5 gms. of oil.

THE ADDITIVE SYSTEM (a) The detergent inhibitor One of the components of the additive system utilized in the formation of the high viscosity index multi-viscosity grade lubricant oil which serves as a base for the compositions of this invention is a detergent inhibitor. Generally speaking, this additive maintains deposit particles and sludge in suspension in the oil and thus prevents their deposition on moving parts being lubricated. Preferred among the operable detergent inhibitors are (1) alkaline earth metal salts of C C (preferably c -c alkyl phenol sulfides, (2) phosphosulfurized derivatives of (l), (3) alkaline earth metal aromatic hydrocarbon sulfonates having molecular weights of about 800 to 1000 and (4) mixtures of (1), (2) and (3). Especially preferred are the oil-soluble basic calcium and barium salts of nonyl phenol sulfide (including their P 8 treated derivatives) combined with oil-soluble calcium petroleum sulfonate. An outstanding material is formed by reacting a phosphorus sulfide with a polymer of isobutylene and further reacting this material with a mixture of a high alkalinity calcium salt of a nonyl phenol sulfide and a calcium petroleum sulfonate. The detergent inhibitor is used in amounts varying between about 0.5 and 10 wt. percent (based on total composition), with 1 to 3% being especially preferred. Although there are set out above preferred detergent inhibitors, it is to be understood that other additives having detergent properties are operable, such as P 8 treated polybutenes and alkyl phenates of alkaline earth metals, etc.

(b) The antioxidant agent Antioxidants which also provide extreme pressure resistance and inhibition of the corrosion of lead in copperlead bearings are supplied by means of a phosphorus and sulfur containing additive such as metal salts of dialkyl dithiophosphoric acids, sulfurized terpenes, phosphosulfurized terpenes, etc. Especially preferred are the zinc salts of di(C C alkyl) dithiophosphoric acid. These materials are used in amounts of between about 0.1 and 5%, preferably between about 0.5 and 1.5%, percentage being by weight, based on total composition.

(0) The pour point depressor amounts up to about 5.0 wt. percent may be employed.) Other pour point depressants may be used such as dibasic acid ester polymers and copolymers of unsaturated dibasic acid esters with other unsaturates such as styrene, vinyl acetate and the like, e. g., a copolymer of C fumarate With vinyl acetate.

(d) The viscosity index improver The concept of the multi-viscosity grade oils, as was explained above, is based on the use of a light, mineral oil base stock which has been thickened to the desirable viscosity range with large amounts of a viscosity index improver. It has been found that from about 0.5 to

about 5.0%, preferably about 1.0 to about 3.0% of poly- Inerized isobutylene having a molecular weight within the range of about 15,000 to 20,000 Staudinger is highly efiicaci'ous. This viscosity index improver is highly stable to the shearing forces present in reciprocating engines and is contemplated in the preferred embodiment. Other well-known viscosity index improvers may be used, however, among which may be mentioned polystyrene, polymethacrylic acid esters (described above under pour point depressants), polyacrylic acid esters and polyvinyl acetate-alkyl fumarate polymers.

The base material for the compositions of this invention comprising a light mineral oil distillate and the additive system is improved against intake valve deposits by the addition of from about 0.5 to 30.0%, preferably about 1.0 to about 15.0 weight percent of the branched chain esters of the polylinoleic acids described above. A particularly eifective concentration is about 3 to 6 wt. percent. The final compositions are prepared simply by admixing the ester with the base oil, the former being completely compatible with the latter. Esters of the dimer of linoleic acid are particularly preferred.

In accordance with the concept of this invention, several embodiments were prepared and tested for intake valve deposit reduction. The test utilized to give an indication of the deposit forming tendency of the final blends was the Homelite engine test. This test utilizes the two cycle Homelite engine in which gasoline containing the test lubricant is swept across the hot piston underside in a manner analogous to the way gasoline vapors sweep across the hot intake valves in an automotive four-cycle engine. The deposit demerits obtained in this test have been found to correlate extremely well with those obtained in full-scale field tests.

Lubricating oil compositions containing dimerates/trimerates were subjected to the Homelite engine test. The data resulting from these tests are set out in Tables I and II below. For purposes of comparison, Table III presents Homelite engine test results obtained with other lubricant compositions. The following base oils of commercial 10W-30 grade were employed in these tests:

Base oil A (30 API gravity):

Lubricating oil I Additive A (V. I. improver) Additive B (detergent-inhibitor) Additive C (V. I. improver-pour point depressant Additive D (antioxidant) Volume percent 80.0

More particularly, the components of the base oils were as follows:

Lubricating oil I was a solvent extracted and dewaxed mineral oil distillate boiling below about 600 F. at 10 mm. Hg, having an SSU viscosity at 100 F. of about 100 and a resinification index of aboutS.

Lubricating oil-II- was a solvent extracted and dewaxed mineral oil distillate boiling below about 675 F. at 10 mm. Hg, having an SSU viscosity at 100 F. of about 170 and a resinification index of about 16.

Additive A was an additive concentrate containing about wt. percent of'polyisobutylene of about 18,000

molecular weight.

Additive B was an additive concentrate containing (1) 37.5% by volume of a concentrate containingabout 40 wt. percent of calcium alkyl benzene sulfon'ate of about 870 molecular weight, and ('2') about 62.5%. by volume of a concentrate containing about 40 wt. percent of P 8 treated barium iso-nonyl phenol sulfide.

Additive C was an additive concentrate containing about 45 wt. percent of poly C C metha'cry late .of about 20,000 molecular weight (sold under the: trade name of Acryloid 747).

Additive D was an additive concentrate containing about wt. percent of zinc di (C -C dithiophosphate (sold under the trade name of Lubrizol 1060-).

The balance of the additive concentrate described above was a mineral lubricating oil.

TABLE 1.HOMELITE ENGINE TEST RESULTS USING BASE OIL A AND DIM-ERATE/TRIMERATE Composition tested Piston demerit Weight percent Ra se Weight percent dimerate/trimerate 5 hrs. 20.hrs.

100 3.0 8.0 5 (Ca 0x0 dimerate) l]. 5 1.25 95. 5 (Ca 0x0 trimerate) 1. 0 l. 5 95 5 (04 0x0 dimerate) 1. 8 3. 0

1 Present invention.

TABLE II.HOMELITE ENGINE TEST RESULTS USING BASE OIL B AND DIMERATE Composition tested Piston demerit Weight perceni.1 1013.56 Weight percent dimerate 5 hrs. 20 hrs.

1. 50 2. 25 5 (C8 0x0 dimerate) 0125 0.50 5 (C13 0x0 dimeratefl... 0.50 0. 75 1 (Cir Oxo'dimeratefl- 1. 25 1. 50

1 Present invention.

TABLE III.HOMELITE ENGINE TEST RESULTS USING BASE OIL A AND ITHER ADDI'IIVES Composition tested Piston demerit Weight percent base Weight percent additive 5 hrs. 20 hrs.

oil A 3. 0 3.0 5 (diethyl phthalate) 1. 8 2. 5 5 (isopropyl oleate) 2. 5 6 (di-2-ethyl hexyl sebacate) 1. 5 3.0 5 (methoxy ethyl acetyl rieinoleate) 2.8 5 (sorbitan monooleate 2. 5

5 (triethylene glycol di-2-ethyl hexoate) 1. 5 2. 8

It will be seen from examination of the data of Tables I and II above that a substantial reduction in the deposit forming tendency of multi-viscosity grade lubricating oils is obtained by the inclusion therein of from 1 to 5 Wt. percent of C and C esters of polylinoleic acid. Table I shows that an isobutyl alcohol ester of dimer acid is unsatisfactory since it does not reduce the demerit rating sufliciently in the 20-hour test. Table III contains comparable data on blends of the base materials containing 5% of other types of well-known esters described "7 in the prior art as additives for lubricating oils. It is seen from the data in Table III that these other esters have little or no eifect in reducing the deposit forming tendencies of the base oil.

A lubricating oil composition of the present invention was also evaluated in a Chrysler Test carried out for a period of 50-100 hours at 2500 R. P. M. and no load using a 1951 Chrysler engine. In this test base oil A (described heretofore) gave an intake valve underside demerit of 2.1 after 50 hours and 3.6 after 100 hours. The lubricating oil composition of the present invention containing 95 vol. percent of base oil A and 5 vol. percent of C Oxo dimerate gave an intake valve underside demerit of only 2.4 after 100 hours. Another composition of the present invention gave an intake valve underside demerit of only 0.25 after 50 hours and 0.59 after 100 hours. This second composition of the present invention had the following formulation:

To summarize briefly, the instant invention relates to a method of improving the deposit forming tendencies of multi-viscosity grade lubricating oil compositions. It has been found and forms the subject of this invention that the addition of from about 0.5 to about 30.0 weight percent of the C -C highly branched chain primary aliphatic alcohol esters of polylinoleic acid greatly improves these lubricating oil compositions in this respect. The compositions contemplated by this invention therefore comprise an extracted mineral oil distillate having a boiling range within the range of from about 300 to about 700 F. (at 10 mm. Hg) and having a resinification index below about 20 mg./5 grns. of oil, and an additive system comprising a detergent inhibitor, an antioxidant, a pour point depressor and a viscosity index improver containing combined therein a minor but deposit forming tendency reducing amount of a material selected from the group consisting of the C to C highly branched chain primary aliphatic alcohol esters of the dimer and trimer of linoleic acid.

What is claimed is:

1. An improved lubricating oil composition having reduced deposit forming tendencies which comprises a major proportion of an extracted mineral lubricating oil boiling within the range of about 375 to 675 F. at 10 mm. Hg and having a resinification index below about 20 mg./5 gms. of oil, about 0.5 to 10 wt. percent of a detergent selected from the group consisting of alkaline earth metal salts of C -C alkyl phenol sulfides and their phosphosulfurized derivatives and alkaline earth metal aromatic hydrocarbon sulfonates having molecular weights of about 800 to 1000, about 0.1 to 5 wt. percent of zinc di (C -C alkyl)dithiophosphate, about 0.005 to 5.0 wt. percent of 012-01 methacrylate polymer of 15,000 to 25,000 molecular Weight, and an ester selected from the group consisting of the C to C branched chain primary aliphatic alcohol esters of the dimer and trimer of linoleic acid.

2. Composition according to claim 1 which also contains about 0.5 to 5.0 wt. percent of polyisobutylene of about 15,000 to 20,000 molecular weight.

3. Composition according to claim 1 wherein said ester is the ester of C branched chain primary alcohol and the dimer acid of linoleic acid.

4. Composition according to claim 1 wherein said ester is the ester of C branched chain primary alcohol and the trimer acid of linoleic acid.

5. Composition according to claim 1 wherein said ester is the ester of C branched chain primary alcohol and the dimer acid of linoleic acid.

6. Composition according to claim 1 wherein said ester is the ester of C branched chain primary alcohol and the trimer acid of linoleic acid.

References Cited in the file of this patent UNITED STATES PATENTS 2,197,153 Merrill Apr. 16, 1940 2,325,040 Cook et al. July 27, 1943 2,342,113 Blair Feb. 22, 1944 2,365,919 Uloth et a1. Dec. 26, 1944 2,411,178 Young et al. Nov. 19, 1946 2,429,219 Cowan et al. Oct. 21, 1947 2,631,979 McDermott Mar. 17, 1953 2,632,695 Landis et a1. Mar. 24, 1953 2,673,184 Morway et a1. Mar. 23, 1954 2,718,503 Rocchini Sept. 20, 1955 2,755,251 Barker July 17, 1956 

1. AN IMPROVED LUBRICATING OIL COMPOSITION HAVING REDUCED DEPOSIT FORMING TENDENCIES WHICH COMPRISES A MAJOR PROPORTIONM OF AN EXTRACTED MINERL LUBRICATING OIL BOILING WITHIN THE RANGE OF ABOUT 375* TO 675*F. AT 10 MM. HG AND HAVING A RESINIFICATION INDEX BELOW ABOUT 20 MG./5 GMS. OF OILS, ABOUT 0.5 TO 10 WT. PERCENT OF A DETERGENT SELECTED FROM THE GROUP CONSISTONG OF ALKALINE EARTH METAL SALDTS OF C4-C24 ALKYL PHENOL SULFIDES AND THEIR PHOSPHOSULFURIZED DERIVATIES AND ALKALINE EARTH METAL AROMATIC HYDROCARBON SULFONATES HAVING MOLECULAR WEIGHTS OF ABOUT 800 TO 1000, ABOUT 0.1 TO 5 WT. PERCENT OF ZINC DI (C3-C12 ALKYL)DITHIOPHOSPHATE, ABOUT 0.005 TO 5.0 WT. PERCENT OF C12-C18 METHACRYLATE POLUMER OF 15,000 TO 25,000 MOLECULAR WEIGHT, AND AN ESTER SELECTED FROM THE GROUP CONSISTING OF THE 47 TO C14 BRANCHED CHAIN PRIMARY ALIPHATIC ALCOHOL ESTERS OF THE DIMER AND TRIMER OF LINOLEIC ACID. 